Combination of fluid loss control additive and lost circulation materials to control losses in formation

ABSTRACT

Provided are methods, compositions, and systems embodying cement compositions and the synergistic effect of lost circulation materials (LCMs) and fluid loss control additives (FLCAs) thereupon for cementing subterranean zones. A method of subterranean well cementing, comprising providing a cement composition comprising a hydraulic cement, a first FLCA, a LCM, and water, wherein the first FLCA comprises a water-soluble polymer with repeating units comprising a 5- to 6-membered cyclic amide; introducing the cement composition into a wellbore penetrating a subterranean formation, wherein inclusion of the first FLCA and the LCM in the cement composition fluid reduces fluid loss into the subterranean formation, wherein the subterranean formation has fractures with a width of from about 1 micron to about 800 microns, and wherein the subterranean formation has a permeability of about 1 millidarcy to about 300 Darcy; and allowing the cement composition to set in the subterranean formation.

BACKGROUND

Subterranean zones penetrated by drilling wellbores are commonly sealedby cement compositions. For example, cement compositions are used inprimary cementing operations whereby pipe strings, such as casing andliners, are cemented in wellbores. In a typical primary cementingoperation, a cement composition may be pumped into an annulus betweenthe exterior surface of the pipe string disposed therein and the wallsof the wellbore, or a larger conduit in the wellbore. The cementcomposition may set in the annular space, thereby forming a cementsheath. Generally, a cement sheath is an annular sheath of hardened,substantially impermeable material that may support and position thepipe string in the wellbore and may bond the exterior surface of thepipe string to the wellbore walls, or the larger conduit. Among otherthings, the cement sheath surrounding the pipe string should function toprevent the migration of drilling fluids in the annulus, as well asprotecting the pipe string from corrosion. Cement compositions may alsobe utilized in a variety of cementing operations, such as sealing highlypermeable zones or fractures in subterranean zones, plugging cracks orholes in pipe strings, and the like.

Subterranean formations traversed by well bores often may be weak,highly permeable, and extensively fractured. In some cases, suchformations may be unable to withstand the hydrostatic pressure normallyassociated with fluids (e.g., cement compositions and the like) beinginjected into the formation. In such cases, the hydrostatic pressure maybe sufficient to force such fluids into the natural or created fracturesand/or permeable zones of the formation, which may result in asignificant loss of fluid into the formation. This loss of fluidcirculation may be problematic for a number of reasons. For example,where the loss of circulation occurs during a cementing operation,excessive fluid loss may cause a cement composition to dehydrateprematurely. Premature dehydration of the cement composition mayexcessively viscosify the cement composition, and potentially may causean operator to terminate the cementing operation, wash out the cementcomposition from the well bore, and restart the cementing operationanew.

Previous attempts to minimize the loss of circulation into thesubterranean formation have involved adding a variety of additives,including, but not limited to, asphaltenes, ground coal, cellulosicmaterials, plastic materials, walnut hulls, plastic laminates (Formica®laminate), and the like, to the cement composition. Fluid loss additivesmay also be included in cement composition to combat fluid loss into theformation. While attempts have been made previously to address problemswith loss of fluid into the formation, these materials may notadequately address problems with loss of fluid, for example, due tovaried fracture sizes or permeability that can be encountered downhole.For instance, existing attempts for controlling loss of fluid may onlybe effective at addressing loss of fluid into certain fracture sizes.

BRIEF DESCRIPTION OF THE DRAWINGS

These drawings illustrate certain aspects of some of the examples of thepresent disclosure and should not be used to limit or define thedisclosure.

FIG. 1 is a schematic illustration of an example system for thepreparation and delivery of a cement composition to a wellbore.

FIG. 2 is a schematic illustration of example surface equipment that maybe used in the placement of a cement composition in a wellbore.

FIG. 3 is a schematic illustration of the example placement of a cementcomposition into a wellbore annulus.

DETAILED DESCRIPTION

The present disclosure provides methods, compositions, and systemsembodying cement compositions and the synergistic effect of lostcirculation materials (LCMs) and fluid loss control additives (FLCAs)thereupon for cementing subterranean zones.

The cement compositions may include a hydraulic cement, LCMs, a firstFLCA (FLCA-1), and water. Optionally, a second FLCA (FLCA-2) may beincluded in the cement compositions. The cement composition results inthe synergistic effect of LCMs and FLCAs to improve the capability of acement composition's ability to plug a subterranean formation withvarying fracture widths, for example, having widths from about 1 micronto about 800 microns and permeability of from about 1 milliDarcy (mD) toabout 300 Darcy. Alternatively, the subterranean formation may havefracture widths varying from about 1 micron to about 800 microns, about20 microns to about 700 microns, about 50 microns to about 600 microns,about 100 microns to about 500 microns, or about 200 microns to about400 microns. Moreover, alternatively, the subterranean formation mayhave a permeability of from about 1 mD to about 300 Darcy, about 1 Darcyto about 250 Darcy, about 50 Darcy to about 200 Darcy, or about 100Darcy to about 150 Darcy. Currently used LCMs may be effective for usein curing fractures, whereas, they have not shown to be effective foruse in plugging a permeable formation. However, the compositiondisclosed herein may be used to effectively cure fractures and plug thepermeable formation. In the permeable formation, the particles andcompositions disclosed herein form a layer within the permeable zone,then the interstitial space between the particles of the disclosedcomposition may be plugged by the disclosed FLCAs.

Any of a variety of hydraulic cements may be suitable for the disclosedcomposition, including those including calcium, aluminum, silicon,oxygen, iron, and/or sulfur, which set and harden by reaction withwater. Specific examples of hydraulic cements that may be suitableinclude, but are not limited to, Portland cements, pozzolana cements,gypsum cements, alumina-based cements, silica cements, and anycombination thereof. Examples of suitable Portland cements may includethose classified as Classes A, B, C, G, or H cements according toAmerican Petroleum Institute, API Specification for Materials andTesting for Well Cements, API Specification 10, Fifth Ed., Jul. 1, 1990.Additional examples of suitable Portland cements may include thoseclassified as ASTM Type I, II, III, IV, or V.

The hydraulic cement may be included in the cement composition in anysuitable amount as desired for a particular application. Theconcentration of the hydraulic cement may be selected, for example, toprovide a particular compressive strength for the cement compositionafter setting. Where used, the hydraulic cement may be included in anamount of about 1% to about 80% by weight of the cement composition.Alternatively, the hydraulic cement may be present in an amount of about1% to about 80% by weight of the cement composition, about 5% to about75% by weight of the cement composition, about 10% to about 70% byweight of the cement composition, about 20% to about 60% by weight ofthe cement composition, or about 30% to about 50% by weight of thecement composition. One of ordinary skill in the art, with the benefitof this disclosure, should recognize the appropriate amount of thehydraulic cement to include for a chosen application.

A wide variety of LCMs may be used in the example cement compositionsdisclosed herein. For example, suitable LCMs may include, but are notlimited to, petroleum coke, graphite, walnut hulls, cedar bark, shreddedcane stalks, mineral fiber, mica flakes, cellophane, calcium carbonate,ground rubber, polymeric materials, pieces of plastic, grounded marble,asphaltenes, ground coal, wood, nut hulls, plastic laminates (Formica®laminate), corncobs, cotton hulls, and combinations thereof. In anexample, a suitable LCM includes petroleum coke, graphite, walnut hulls,and graphite. The LCMs may be blended with the hydraulic cement prior tocombination of the dry blend with the water fluid to form the cementcomposition or the LCMs may be added separately to the cementcomposition.

The LCMs may be present in the treatment fluid in any suitable amount,including, but not limited to, an amount of about 0.1% to about 10% byweight of the cement composition. Alternatively, the LCMs may be presentin an amount of about 0.1% to about 10% by weight of the cementcomposition, about 2% to about 9% by weight of the cement composition,about 3% to about 8% by weight of the cement composition, about 4% toabout 7% by weight of the cement composition, or about 5% to about 6% byweight of the cement composition. One of ordinary skill in the art, withthe benefit of this disclosure, should recognize the appropriate amountof the LCMs to include for a chosen application.

The particle size of the LCMs may be selected to synergisticallyfunction with the FLCAs in reducing loss of fluid into the formation.For example, selection of the particle size of the LCM can enable thecombination with the FLCAs to function over a wider range of fracturesizes. The LCMs may have a multimodal particle size distribution(“PSD”). As referenced herein, the PSD of a powder, or granular materialor particles dispersed in fluid, is a list of values or a mathematicalfunction that defines the relative amount, typically by mass, ofparticles present according to size. Generally, PSD may be defined bythe method by which it is determined. A commonly used method ofdetermination is sieve analysis, wherein particles are separated onsieves of different sizes. Sieve analysis presents particle sizeinformation in the form of an S-curve of cumulative mass retained oneach sieve versus the sieve mesh size. Thus, the PSD may be defined interms of discrete size ranges. The PSD may be determined over a list ofsize ranges that cover nearly all the sizes present in a particularsample. Some methods of determination allow much narrower size ranges tobe defined than can be obtained by use of sieves, and may be applicableto particle sizes outside of the range available in sieves.

Moreover, as further disclosed herein, commonly used metrics fordescribing PSD are D-Values (D10, D50 & D90) which are the interceptsfor 10%, 50% and 90% of the cumulative mass. For example, the D10 is thediameter at which 10% of the sample's mass is particles with a diameterless than this value. The D50 is the diameter of the particle that 50%of a sample's mass is particles with a diameter less than this value.The D90 is the diameter at which 90% of the sample's mass is particleswith a diameter less than this value.

Further, the PSD may be expressed as a “range” analysis, in which theamount in each size range may be listed in order. For example, the LCMsmay have a PSD of about 2 microns to about 570 microns. Alternatively,the LCMs may have a PSD of about 2 microns to about 570 microns, about20 microns to about 500 microns, about 30 microns to about 400 microns,about 40 microns to about 300 microns, about 50 microns to about 200microns, or about 100 microns to about 150 microns.

By way of analysis, the multimodal particle size distribution results inmultiple modal peaks. Generally, a multimodal distribution may be acontinuous probability distribution with two or more modes. For example,the LCMs may have from about 2 up to about 20 or more modal peaks.Alternatively, the LCMs may have from about 2 to about 20 or more modalpeaks, from about 4 to about 18 or more modal peaks, from about 6 toabout 16 or more modal peaks, from about 8 to about 14 or more modalpeaks, or from about 10 to about 12 or more modal peaks. Modal peaksoccur on a particle size distribution curve when there are increasedparticle concentrations relative to particle sizes on either side of thecurve. One of ordinary skill in the art, with the benefit of thisdisclosure, should be able to select an appropriate particle size forthe LCMs for a particular application.

The FLCAs included in the cement composition may include a first FLCA(FLCA-1). The FLCA-1 may be a water-soluble polymer with repeating unitsthat include a 5 to 6 membered cyclic amide. The FLCA-1 may be selectedfrom, but not limited to, a group including a polyacryloylmorpholinepolymer, a polyvinylpyrrolidone polymer, and combinations thereof. Forexample, the polymer component of the FLCA-1 may be selected from thegroup including a polyacryloylmorpholine copolymer, apolyvinylpyrrolidone copolymer, and combinations thereof. For example,the polyacryloylmorpholine copolymer may be selected from a groupincluding an acrylic acid and acryloylmorpholine copolymer, amethacrylic acid and acryloylmorpholine copolymer, an acrylamide andacryloylmorpholine copolymer, an N,N-dimethyl acrylamide andacryloylmorpholine copolymer, a 2-acrylamido-2-methylpropane sulfonicacid and acryloylmorpholine copolymer, and combinations thereof. Forexample, the polyacryloylmorpholine copolymer may be a2-acrylamido-2-methylpropane sulfonic acid and acryloylmorpholinecopolymer, and combinations thereof. For example, thepolyvinylpyrrolidone copolymer may be selected from the group of anacrylic acid and vinylpyrrolidone copolymer, a methacrylic acid andvinylpyrrolidone copolymer, an acrylamide and vinylpyrrolidonecopolymer, an N,N-dimethyl acrylamide and vinylpyrrolidone copolymer, a2-acrylamido-2-methylpropane sulfonic acid and vinylpyrrolidonecopolymer, and combinations thereof. For example, thepolyvinylpyrrolidone copolymer may be a 2-acrylamido-2-methylpropanesulfonic acid and vinylpyrrolidone copolymer.

The FLCA-1 may be present in the cement composition in any suitableamount, including, but not limited to, an amount of about 0.05% to about5% by weight of the cement composition. For example, the FLCA-1 may bepresent in an amount of about 0.05% to about 3% by weight of the cementcomposition, about 0.1% to about 1% by weight of the cement composition,or about 0.1% to about 0.5% by weight of the cement composition. One ofordinary skill in the art, with the benefit of this disclosure, shouldbe able to select an appropriate concentration of the FLCA-1 for aparticular application.

The FLCAs included in the cement composition may include a second FLCA(FLCA-2). The FLCA-2 may be a water-soluble polymer component including,but not limited to, a dimethyl group, a sulfomethyl group, a sulfonategroup, and combinations thereof. The FLCA-2 may be selected from, butnot limited to, the group that includes a graft polymer of2-acrylamido-2-methylpropane sulfonic acid and acrylamide. The FLCA-2may further be selected from, but not limited to, the group thatincludes polyacrylamide polymers and copolymers, copolymers of2-Acrylamido-2-methylpropane sulfonic acid and dimethylacrylamide (DMA),polymers of acrylonitrile, isobutylene, acrylamide and2-acrylamido-2-methylpropane sulfonic acid monomers grafted on lignite,acryloylmorpholine and vinylphosphonic acid copolymers, humic acidgrafted polymers, and polymers of polyvinyl alcohol and boric acid, andcombinations thereof.

The FLCA-2 may be present in the cement composition in any suitableamount, including, but not limited to, an amount of about 0.05% to about5% by weight of the cement composition. For example, the FLCA-2 may bepresent in an amount of about 0.05% to about 3% by weight of the cementcomposition, about 0.1% to about 1% by weight of the cement composition,or about 0.1% to about 0.5% by weight of the cement composition. One ofordinary skill in the art, with the benefit of this disclosure, shouldbe able to select an appropriate concentration of the FLCA-2 for aparticular application.

The water may be from any source provided that it does not contain anexcess of compounds that may undesirably affect other components in thecement compositions. For example, a cement composition may include freshwater, saltwater such as brine (e.g., saturated saltwater produced fromsubterranean formations) or seawater, or any combination thereof.Saltwater generally may include one or more dissolved salts therein andmay be saturated or unsaturated as desired for a particular application.Seawater or brines may be suitable for use in some examples of thecement composition. Further, the water may be present in an amountsufficient to form a pumpable slurry.

Generally, the water may be added to the cement composition in anydesired concentration, including about 10% to about 80% by weight of thecement composition. Alternatively, the water may be present in thecement composition in an amount of about 10% to about 80% by weight ofthe cement composition, about 20% to about 70% by weight of the cementcomposition, about 30% to about 60% by weight of the cement composition,or about 40% to about 50% by weight of the cement composition. One ofordinary skill in the art, with the benefit of this disclosure, shouldbe able to select an appropriate amount of water to include in a cementcomposition.

In some embodiments, the cement composition may further include alightweight additive. The lightweight additive may be included to reducethe density of examples of the cement composition. For example, thelightweight additive may be used to form a lightweight cementcomposition, for example, having a density of less than about 13 lb/gal(1558 kg/m³). The lightweight additive typically may have a specificgravity of less than about 2.0. Examples of suitable lightweightadditives may include, but are not limited to, sodium silicate, hollowmicrospheres, gilsonite, perlite, and combinations thereof. Thelightweight additive may be present in an amount of about 0.1% to about15% by weight of the cement composition. Alternatively, the lightweightadditive may be present in an amount of about 0.1% to about 15% byweight of the cement composition, about 1% to about 15% by weight of thecement composition, or about 2% to about 8% by weight of the cementcomposition.

In some embodiments, the cement composition may be foamed and includewater, a gas, and a foaming surfactant. Optionally, to provide a cementcomposition with a lower density and more stable foam, the foamed cementcomposition may further include a lightweight additive, for example. Abase slurry may be prepared that may then be foamed to provide an evenlower density. In some embodiments, the foamed cement composition mayhave a density of about 4 lb/gal (479 kg/m³) to about 13 lb/gal (1558kg/m³, about 5 lb/gal (533 kg/m³) to about 10 lb/gal (1198 kg/m³), orabout 7 lb/gal (839 kg/m³) to about 9 lb/gal (1078 kg/m³).

The gas used in embodiments of the foamed cement composition may be anysuitable gas for foaming the cement composition, including, but notlimited to, air, nitrogen, and combinations thereof. Generally, the gasshould be present in examples of the foamed cement composition in anamount sufficient to form the desired foam. In certain embodiments, thegas may be present in an amount of about 5% to about 80% by volume ofthe cement composition fluid at atmospheric pressure. Alternatively, thegas may be present in an amount of about 5% to about 80% by volume,about 10% to about 70% by volume, about 20% to about 60% by volume, orabout 30% to about 50% by volume.

The foaming surfactant may include any suitable surfactant thatfacilitates the formation of foam, including, but are not limited to:anionic, nonionic, amphoteric (including zwitterionic surfactants),cationic surfactant, or combinations thereof, betaines; anionicsurfactants such as hydrolyzed keratin; amine oxides such as alkyl oralkene dimethyl amine oxides; cocoamidopropyl dimethylamine oxide;methyl ester sulfonates; alkyl or alkene amidobetaines such ascocoamidopropyl betaine; alpha-olefin sulfonates; quaternary surfactantssuch as trimethyltallowammonium chloride and trimethylcocoammoniumchloride; C₈ to C₂₂ alkylethoxylate sulfates; and combinations thereof.Specific examples of suitable foaming surfactants include, but are notlimited to: combinations of an ammonium salt of an alkyl ether sulfate,a cocoamidopropyl betaine surfactant, a cocoamidopropyl dimethylamineoxide surfactant, sodium chloride, and water; combinations of anammonium salt of an alkyl ether sulfate surfactant, a cocoamidopropylhydroxysultaine surfactant, a cocoamidopropyl dimethylamine oxidesurfactant, sodium chloride, and water; hydrolyzed keratin; combinationsof an ethoxylated alcohol ether sulfate surfactant, an alkyl or alkeneamidopropyl betaine surfactant, and an alkyl or alkene dimethylamineoxide surfactant; aqueous solutions of an alpha-olefinic sulfonatesurfactant and a betaine surfactant, combinations of an ammonium salt ofan alkyl ether sulfate, and combinations thereof. Generally, the foamingsurfactant may be present in the cement composition fluids in an amountsufficient to provide a suitable foam. In some embodiments, the foamingagent may be present in an amount of about 0.8% to about 5% by volume ofthe water.

The cement compositions may include a pozzolan such as fly ash, silicafume, metakaolin, volcanic glasses, other natural glasses orcombinations thereof. An example of a suitable pozzolan may include flyash. An additional example of a suitable pozzolan may include a naturalpozzolan. Natural pozzolans are generally present on the Earth's surfaceand set and harden in the presence of hydrated lime and water. Examplesincluding of natural pozzolans may include natural glasses, diatomaceousearth, volcanic ash, opaline shale, tuff, and combinations thereof. Thepozzolan generally may be included in the cement compositions in anamount desired for a particular application. In some examples, thepozzolan may be present in the cement composition in an amount of about1% to about 60% by weight of the cement composition, about 5% to about55% by weight of the cement composition, about 10% to about 50% byweight of the cement composition, about 15% to about 45% by weight ofthe cement composition, about 20% to about 40% by weight of the cementcomposition, or about 25% to about 35% by weight of the cementcomposition. One of ordinary skill in the art, with the benefit of thisdisclosure, should recognize the appropriate amount of the pozzolan toinclude for a chosen application.

The cement composition may include slag. Slag is generally a granulated,blast furnace by-product from the production of cast iron including theoxidized impurities found in iron ore. The slag may be included inexamples of the cement compositions in an amount suitable for aparticular application. The slag may be present in an amount of about0.1% to about 40% by weight of the cement composition. Alternatively,the slag may be present in an amount of about 0.1% to about 40%, about5% to about 35%, about 10% to about 30%, or about 15% to about 25% byweight of the cement composition. One of ordinary skill in the art, withthe benefit of this disclosure, should recognize the appropriate amountof the slag to include for a chosen application.

The cement composition may further include shale in an amountsufficient, for example, to provide the desired compressive strength,density, and/or cost. A variety of shales are suitable, including, butnot limited to, silicon, aluminum, calcium, and/or magnesium. Examplesof suitable shales include vitrified shale and/or calcined shale. Theshale may be included in examples of the cement compositions in anamount suitable for a particular application. The shale may be presentin an amount of about 0.1% to about 40% by weight of the cementcomposition. Alternatively, the shale may be present in an amount ofabout 0.1% to about 40%, about 5% to about 35%, about 10% to about 30%,or about 15% to about 25% by weight of the cement composition. One ofordinary skill in the art, with the benefit of this disclosure, shouldrecognize the appropriate amount of the shale to include for a chosenapplication.

Some examples of the cement compositions may include silica sources,such as crystalline silica and/or amorphous silica. Crystalline silicais a powder that may be included in examples of the cement compositions,for example, to prevent cement compressive strength retrogression.Amorphous silica is a powder that may be included in examples of thecement compositions as a lightweight filler and/or to increase cementcompressive strength. Amorphous silica is generally a byproduct of aferrosilicon production process, wherein the amorphous silica may beformed by oxidation and condensation of gaseous silicon suboxide, SiO,which is formed as an intermediate during the process. Examplesincluding additional silica sources may utilize the additional silicasource as needed to enhance compressive strength or set times.

The cement composition may further include kiln dust. “Kiln dust,” asthat term is used herein, refers to a solid material generated as aby-product of the heating of certain materials in kilns. The term “kilndust” as used herein is intended to include kiln dust made as describedherein and equivalent forms of kiln dust. Depending on its source, kilndust may exhibit cementitious properties in that it can set and hardenin the presence of water. Examples of suitable kiln dusts include cementkiln dust, lime kiln dust, and combinations thereof. Cement kiln dustmay be generated as a by-product of cement production that is removedfrom the gas stream and collected, for example, in a dust collector.Usually, large quantities of cement kiln dust are collected in theproduction of cement that are commonly disposed of as waste. Thechemical analysis of the cement kiln dust from various cementmanufactures varies depending on a number of factors, including theparticular kiln feed, the efficiencies of the cement productionoperation, and the associated dust collection systems. Cement kin dustgenerally may include a variety of oxides, such as SiO₂, Al₂O₃, Fe₂O₃,CaO, MgO, SO₃, Na₂O, and K₂O. Problems may also be associated with thedisposal of lime kiln dust, which may be generated as a by-product ofthe calcination of lime. The chemical analysis of lime kiln dust fromvarious lime manufacturers varies depending on several factors,including the particular limestone or dolomitic limestone feed, the typeof kiln, the mode of operation of the kiln, the efficiencies of the limeproduction operation, and the associated dust collection systems. Limekiln dust generally may include varying amounts of free lime and freemagnesium, limestone, and/or dolomitic limestone and a variety ofoxides, such as SiO₂, Al₂O₃, Fe₂O₃, CaO, MgO, SO₃, Na₂O, and K₂O, andother components, such as chlorides. The kiln dust may be included inexamples of the cement compositions in an amount suitable for aparticular application. In some embodiments, the kiln dust may bepresent in the cement composition in an amount of about 1% to about 60%by weight of the cement composition, about 5% to about 55%, about 10% toabout 50%, about 15% to about 45%, about 20% to about 40%, or about 25%to about 35% by weight of the cement composition. One of ordinary skillin the art, with the benefit of this disclosure, should recognize theappropriate amount of the kiln dust to include for a chosen application.

The cement composition may further include a set retarder. The setretarder may include, but is not limited to, phosphonic acids, such asethylenediamine tetra(methylene phosphonic acid), diethylenetriaminePenta(methylene phosphonic acid), lignosulfonates, such as sodiumlignosulfonate, calcium lignosulfonate, salts such as stannous sulfate,lead acetate, monobasic calcium phosphate, organic acids, such as citricacid, tartaric acid, cellulose derivatives such as hydroxyl ethylcellulose (HEC) and carboxymethyl hydroxyethyl cellulose (CMHEC),synthetic copolymers including sulfonate and carboxylic acid groups suchas sulfonate-functionalized acrylamide-acrylic acid co-polymers; boratecompounds such as alkali borates, sodium metaborate, sodium tetraborate,potassium pentaborate; derivatives thereof, or combinations thereof.Examples of suitable set retarders include, among others, phosphonicacid derivatives. Generally, the set retarder may be present in thecement compositions in an amount sufficient to delay the setting for adesired time. In some embodiments, the set retarder may be present inthe cement compositions in an amount of about 0.01% to about 10% byweight of the cement composition, about 2% to about 8%, or about 4% toabout 6% by weight of the cement composition. One of ordinary skill inthe art, with the benefit of this disclosure, should recognize theappropriate amount of the set retarder to include for a chosenapplication.

The cement composition may include a set accelerator. Suitable setaccelerators may include, but are not limited to, aluminum sulfate,alums, calcium chloride, calcium sulfate, gypsum-hemihydrate, sodiumaluminate, sodium carbonate, sodium chloride, sodium silicate, sodiumsulfate, ferric chloride, or a combination thereof. The set acceleratormay be included in examples of the cement compositions in an amountsuitable for a particular application. In some embodiments, the setaccelerator may be present in the cement compositions in an amount ofabout 0.01% to about 10% by weight of the cement composition, about 2%to about 8%, or about 4% to about 6% by weight of the cementcomposition. One of ordinary skill in the art, with the benefit of thisdisclosure, should recognize the appropriate amount of the setaccelerator to include for a chosen application.

The cement composition may include a dispersant. Suitable dispersantsinclude, but are not limited to, sulfonated-formaldehyde-baseddispersants (e.g., sulfonated acetone formaldehyde condensate) andpolycarboxylated ether dispersants. The dispersant may be included inexamples of the cement compositions in an amount suitable for aparticular application. In some embodiments, a dispersant may beincluded in the cement compositions in an amount of about 0.01% to about5% by weight of the cement composition, about 1% to about 4%, or about2% to about 3% by weight of the cement composition. One of ordinaryskill in the art, with the benefit of this disclosure, should recognizethe appropriate amount of the dispersant to include for a chosenapplication.

The cement composition may include a free water control additive.Suitable free water control additives include, but are not limited to,bentonite, amorphous silica, hydroxyethyl cellulose, and combinationsthereof. The free water control additive may be provided as a dry solidin some embodiments. The free water control additive may be included inexamples of the cement compositions in an amount suitable for aparticular application. The free water control additive may be presentin an amount of about 0.1% to about 16% by weight of dry solids, about2% to about 14%, about 4% to about 12%, about 6% to about 10%, or about7% to about 9% by weight of dry solids. One of ordinary skill in theart, with the benefit of this disclosure, should recognize theappropriate amount of the free water control additive to include for achosen application.

Other additives suitable for use in subterranean cementing operationsalso may be included in embodiments of the cement compositions. Examplesof such additives include, but are not limited to weighting agents,gas-generating additives, mechanical-property-enhancing additives,filtration-control additives, defoaming agents, thixotropic additives,and combinations thereof. In some embodiments, one or more of theseadditives may be dry blended with the hydraulic cement prior to blendingwith water. A specific example of an additional additive may includeclay. A person having ordinary skill in the art, with the benefit ofthis disclosure, should readily be able to determine the type and amountof additive useful for a particular application and desired result.

The cement composition may have a density suitable for a particularapplication. By way of example, the cement composition may have adensity of about 4 pounds per gallon (“lb/gal”) (479 kg/m³) to about 20lb/gal (2396 kg/m³). Alternatively, the cement composition may have adensity of about 4 lb/gal (479 kg/m³) to about 20 lb/gal (2396 kg/m³),about 7 lb/gal (839 kg/m³) to about 16 lb/gal (1917 kg/m³), or about 10lb/gal (1198 kg/m³) to about 13 lb/gal (1558 kg/m³). The density ofcement may be an important design factor as the density range of cementmay be limited by the formation properties. Embodiments of theset-delayed cement compositions may be foamed or unfoamed or may includeother means to reduce their densities, such as lightweight additives.Those of ordinary skill in the art, with the benefit of this disclosure,should recognize the appropriate density for a particular application.

In some embodiments, the cement compositions may set to have a desirablecompressive strength. Compressive strength is generally the capacity ofa material or structure to withstand axially directed pushing forces.The compressive strength may be measured at a specified time after thecement composition has been activated and the resultant composition ismaintained under specified temperature and pressure conditions.Compressive strength can be measured by either destructive ornon-destructive methods. The destructive method physically tests thestrength of treatment fluid samples at various points in time bycrushing the samples in a compression-testing machine. The compressivestrength is calculated from the failure load divided by thecross-sectional area resisting the load and is reported in units ofpound-force per square inch (psi). Non-destructive methods may employ aUSA™ ultrasonic cement analyzer, available from Fann® InstrumentCompany, Houston, Tex. Compressive strength values may be determined inaccordance with API RP 10B-2, Recommended Practice for Testing WellCements, First Edition, July 2005. By way of example, the cementcompositions may develop a 24-hour compressive strength in the range offrom about 50 psi to about 5000 psi, alternatively, from about 100 psito about 4500 psi, or alternatively from about 500 psi to about 4000psi. In some examples, the cement compositions may develop a compressivestrength in 24 hours of at least about 50 psi, at least about 100 psi,at least about 500 psi, or more. In some examples, the compressivestrength values may be determined using destructive or non-destructivemethods at a temperature ranging from 100° F. to 200° F.

The exemplary cement compositions disclosed herein may be used in avariety of subterranean operations, including primary and remedialcementing. The cement composition may be introduced into a wellbore andallowed to set therein. As used herein, introducing the cementcomposition into a subterranean formation includes introduction into anyportion of the subterranean formation, including, without limitation,into a wellbore drilled into the subterranean formation, into a nearwellbore region surrounding the wellbore, such as a subterraneanformation, or into both. In primary cementing, the cement compositionmay be introduced into an annular space between a conduit located in awellbore and the walls of a wellbore (and/or a larger conduit in thewellbore), wherein the wellbore penetrates the subterranean formation.The cement composition may be allowed to set in the annular space toform an annular sheath of hardened cement. The cement composition mayform a barrier that prevents the migration of fluids in the wellbore.The cement composition may also, for example, support the conduit in thewellbore. In remedial cementing, a cement composition may be used, forexample, in squeeze-cementing operations or in the placement of cementplugs. In some embodiments, the composition may be placed in a wellboreto plug an opening (e.g., a void or crack) in the formation, in a gravelpack, in the conduit, in the cement sheath, and/or between the cementsheath and the conduit (e.g., a microannulus).

The components of the cement composition may be combined in any orderdesired to form a cement composition that can be placed into asubterranean formation. In addition, the components of the cementcompositions may be combined using any mixing device compatible with thecomposition, including a bulk mixer, for example. In some embodiments,the cement composition may be prepared by dry blending the solidcomponents of the cement composition at a bulk plant, for example, andthereafter combining the dry blend with water when desired for use.

The systems, methods, and compositions may include any of the variousfeatures disclosed herein, including one or more of the followingstatements.

Statement 1. A method of subterranean well cementing may be disclosed.The method may include providing a cement composition including ahydraulic cement, a first fluid loss control additive, a lostcirculation material, and water, wherein the first fluid loss controladditive may include a water-soluble polymer with repeating unitsincluding a 5- to 6-membered cyclic amide. The method may furtherinclude introducing the cement composition into a wellbore penetrating asubterranean formation, wherein inclusion of the first fluid losscontrol additive and the lost circulation material in the cementcomposition reduces fluid loss into the subterranean formation, whereinthe subterranean formation has fractures with a width of from about 1micron to about 800 microns, and wherein the subterranean formation hasa permeability of about 1 milliDarcy to about 300 Darcy. The method mayfurther include allowing the cement composition to set in thesubterranean formation.

Statement 2. The method of statement 1, wherein the water-solublepolymer of the first fluid loss control additive may include apolyacryloylmorpholine polymer.

Statement 3. The method of statement 1, wherein the water-solublepolymer of the first fluid loss control additive may include apolyvinylpyrrolidone polymer.

Statement 4. The method of statement 1, wherein the water-solublepolymer of the first fluid loss control additive may include apolyacryloylmorpholine copolymer selected from the group consisting ofan acrylic acid and acryloylmorpholine copolymer, a methacrylic acid andacryloylmorpholine copolymer, an acrylamide and acryloylmorpholinecopolymer, an N,N-dimethyl acrylamide and acryloylmorpholine copolymer,and combinations thereof.

Statement 5. The method of statement 1, wherein the water-solublepolymer of the first fluid loss control additive may include apolyvinylpyrrolidone copolymer selected from the group consisting of anacrylic acid and vinylpyrrolidone copolymer, a methacrylic acid andvinylpyrrolidone copolymer, an acrylamide and vinylpyrrolidonecopolymer, an N—N-dimethyl acrylamide and vinylpyrrolidone copolymer,and combinations thereof.

Statement 6. The method of any one of statements 1 to 5, wherein thelost circulation material has a particle size distribution of from about2 microns to about 570 microns.

Statement 7. The method of any one of 1 to 6, wherein the cementcomposition further may include a second fluid loss control additive.

Statement 8. The method of statement 7, wherein the second fluid losscontrol additive may include a water-soluble polymer that includes adimethyl group, a sulfomethyl group, a sulfonate group, and combinationsthereof.

Statement 9. The method of claim 7, wherein the second fluid losscontrol additive includes a graft polymer of 2-acrylamido-2methylpropanesulfonic acid and acrylamide.

Statement 10. The method of any one of claims 1 to 9, wherein the lostcirculation material may include petroleum coke, calcium carbonate,graphite, and walnut hulls.

Statement 11. The method of Statement 1, wherein the water-solublepolymer of the first fluid loss control additive may include apolyacryloylmorpholine polymer, wherein the lost circulation materialmay include petroleum coke, calcium carbonate, graphite, and walnuthulls, wherein the cement composition may include a second fluid losscontrol additive, and wherein the second fluid loss control additive mayinclude a water-soluble polymer including at least one unit selectedfrom the group consisting of a dimethyl group, a sulfomethyl group, asulfonate group, and combinations thereof.

Statement 12. A method of subterranean well cementing may be disclosed.The method may include providing a cement composition that may include ahydraulic cement, a first fluid loss control additive, a second fluidloss control additive, a lost circulation material, and water, whereinthe first fluid loss control additive may include a water-solublepolymer with repeating units including a 5- to 6-membered cyclic amide,wherein the second fluid loss control additive may include awater-soluble polymer including at least one unit selected from thegroup consisting of a dimethyl group, a sulfomethyl group, a sulfonategroup, and combinations thereof, and wherein the lost circulationmaterial has a particle size distribution of from about 2 microns toabout 570 microns. The method may further include introducing the cementcomposition into an annular space surrounding a conduit positioned in asubterranean formation, wherein inclusion of the first fluid losscontrol additive, the second fluid loss control additive, and the lostcirculation material in the cement composition reduces fluid loss intothe subterranean formation, wherein the subterranean formation hasfractures with a width of from about 1 micron to about 800 microns, andwherein the subterranean formation has a permeability of about 1milliDarcy to about 300 Darcy. The method may further include allowingthe cement composition to set in the annular space.

Statement 13. The method of statement 12, wherein the water-solublepolymer of the first fluid loss control additive may include apolyacryloylmorpholine polymer.

Statement 14. The method of statement 12, wherein the water-solublepolymer of the first fluid loss control additive may include apolyvinylpyrrolidone polymer.

Statement 15. The method of any one of statements 12 to 14, wherein thesecond fluid loss control additive is selected from the group consistingof polyacrylamide, an acrylamide copolymer, a copolymer of2-acrylamido-2methylpropane sulfonic acid and dimethylacrylamide,acrylamide and 2-acrylamido-2methylpropane sulfonic acid monomersgrafted on lignite, acryloylmorpholine and vinylphosphonic acidcopolymers, and combinations thereof.

Statement 16. The method of any one of statements 12 to 15, wherein thelost circulation material has a particle size distribution of from about30 microns to about 400 microns.

Statement 17. The method of any one of statements 12 to 16, wherein thelost circulation material may include petroleum coke, calcium carbonate,graphite, and walnut.

Statement 18. A cement composition may be disclosed. The cementcomposition may include a hydraulic cement. The cement composition mayfurther include a first fluid loss additive that may include awater-soluble polymer with repeating units including a 5- to 6-memberedcyclic amide. The cement composition may further include a second fluidloss control additive that may include a water-soluble polymer includingat least one repeating unit selected from the group consisting of adimethyl group, a sulfomethyl group, a sulfonate group, and combinationsthereof. The cement composition may further include a lost circulationmaterial having a particle size distribution of from about 2 microns toabout 570 microns. The cement composition may further include water.

Statement 19. The cement composition of statement 18, wherein thehydraulic cement is selected from the group consisting of a Portlandcement, a pozzolana cement, a gypsum cement, an alumina-based cement, asilica cements, and combinations thereof.

Statement 20. The cement composition of claim 18, wherein thewater-soluble polymer of the first fluid loss control additive mayinclude a polyvinylpyrrolidone copolymer selected from the groupconsisting of an acrylic acid and vinylpyrrolidone copolymer, amethacrylic acid and vinylpyrrolidone copolymer, an acrylamide andvinylpyrrolidone copolymer, an N—N-dimethyl acrylamide andvinylpyrrolidone copolymer, and combinations thereof.

Example methods of using the LCMs and FLCAs in well cementing will nowbe described in more detail with reference to FIGS. 1-3 . FIG. 1illustrates an example system 5 for preparation of a cement compositionincluding LCM and FLCAs and delivery of the cement composition to awellbore. The cement composition may be any cement composition disclosedherein. As shown, the cement composition may be mixed in mixingequipment 10, such as a jet mixer, re-circulating mixer, or a batchmixer, for example, and then pumped via pumping equipment 15 to thewellbore. In some examples, the mixing equipment 10 and the pumpingequipment 15 may be disposed on one or more cement trucks as will beapparent to those of ordinary skill in the art. In some examples, a jetmixer may be used, for example, to continuously mix a dry blendincluding the cement composition, for example, with the water as it isbeing pumped to the wellbore.

An example technique for placing a cement composition into asubterranean formation will now be described with reference to FIGS. 2and 3 . FIG. 2 illustrates example surface equipment 20 that may be usedin placement of a cement composition. It should be noted that while FIG.2 generally depicts a land-based operation, those skilled in the artwill readily recognize that the principles described herein are equallyapplicable to subsea operations that employ floating or sea-basedplatforms and rigs, without departing from the scope of the disclosure.As illustrated by FIG. 2 , the surface equipment 20 may include acementing unit 25, which may include one or more cement trucks. Thecementing unit 25 may include mixing equipment 10 and pumping equipment15 (e.g., FIG. 1 ) as will be apparent to those of ordinary skill in theart. The cementing unit 25 may pump a cement composition 30, which mayinclude water and a cement composition including LCM and FLCAs, througha feed pipe 35 and to a cementing head 36 which conveys the cementcomposition 30 downhole.

Turning now to FIG. 3 , the cement composition 30, including LCM andFLCAs, may be placed into a subterranean formation 45. As illustrated, awellbore 50 may be drilled into one or more subterranean formations 45.While the wellbore 50 is shown extending generally vertically into theone or more subterranean formation 45, the principles described hereinare also applicable to wellbores that extend at an angle through the oneor more subterranean formations 45, such as horizontal and slantedwellbores. As illustrated, the wellbore 50 includes walls 55. In theillustrated example, a surface casing 60 has been inserted into thewellbore 50. The surface casing 60 may be cemented to the walls 55 ofthe wellbore 50 by cement sheath 65. In the illustrated example, one ormore additional conduits (e.g., intermediate casing, production casing,liners, etc.), shown here as casing 70 may also be disposed in thewellbore 50. As illustrated, there is a wellbore annulus 75 formedbetween the casing 70 and the walls 55 of the wellbore 50 and/or thesurface casing 60. One or more centralizers 80 may be attached to thecasing 70, for example, to centralize the casing 70 in the wellbore 50prior to and during the cementing operation.

With continued reference to FIG. 3 , the cement composition 30 may bepumped down the interior of the casing 70. The cement composition 30 maybe allowed to flow down the interior of the casing 70 through the casingshoe 85 at the bottom of the casing 70 and up around the casing 70 intothe wellbore annulus 75. The cement composition 30 may be allowed to setin the wellbore annulus 75, for example, to form a cement sheath thatsupports and positions the casing 70 in the wellbore 50. While notillustrated, other techniques may also be utilized for introduction ofthe cement composition 30. By way of example, reverse circulationtechniques may be used that include introducing the cement composition30 into the subterranean formation 45 by way of the wellbore annulus 75instead of through the casing 70.

As it is introduced, the cement composition 30 may displace other fluids90, such as drilling fluids and/or spacer fluids that may be present inthe interior of the casing 70 and/or the wellbore annulus 75. At least aportion of the displaced fluids 90 may exit the wellbore annulus 75 viaa flow line 95 and be deposited, for example, in one or more retentionpits 100 (e.g., a mud pit), as shown on FIG. 2 . Referring again to FIG.3 , a bottom plug 105 may be introduced into the wellbore 50 ahead ofthe cement composition 30, for example, to separate the cementcomposition 30 from the other fluids 90 that may be inside the casing 70prior to cementing. After the bottom plug 105 reaches the landing collar110, a diaphragm or other suitable device should rupture to allow thecement composition 30 through the bottom plug 105. In FIG. 3 , thebottom plug 105 is shown on the landing collar 110. In the illustratedexample, a top plug 115 may be introduced into the wellbore 50 behindthe cement composition 30. The top plug 115 may separate the cementcomposition 30 from a displacement fluid 120 and push the cementcomposition 30 through the bottom plug 105.

The exemplary cement compositions including LCM and FLCAs disclosedherein may directly or indirectly affect one or more components orpieces of equipment associated with the preparation, delivery,recapture, recycling, reuse, and/or disposal of the LCM and FLCAs andassociated cement compositions. For example, the LCM and FLCAs maydirectly or indirectly affect one or more mixers, related mixingequipment, mud pits, storage facilities or units, compositionseparators, heat exchangers, sensors, gauges, pumps, compressors, andthe like used generate, store, monitor, regulate, and/or recondition thecement compositions including LCM and FLCAs and fluids containing thesame. The disclosed LCM and FLCAs may also directly or indirectly affectany transport or delivery equipment used to convey the LCM and FLCAs toa well site or downhole such as, for example, any transport vessels,conduits, pipelines, trucks, tubulars, and/or pipes used tocompositionally move the LCM and FLCAs from one location to another, anypumps, compressors, or motors (e.g., topside or downhole) used to drivethe LCM and FLCAs, or fluids containing the same, into motion, anyvalves or related joints used to regulate the pressure or flow rate ofthe LCM and FLCAs (or fluids containing the same), and any sensors(i.e., pressure and temperature), gauges, and/or combinations thereof,and the like. The disclosed LCMs and FLCAs may also directly orindirectly affect the various downhole equipment and tools that may comeinto contact with the LCMs and FLCAs such as, but not limited to,wellbore casings, wellbore liner, completion string, insert strings,drill string, coiled tubing, slickline, wireline, drill pipe, drillcollars, mud motors, downhole motors and/or pumps, cement pumps,surface-mounted motors and/or pumps, centralizers, terrorizers,scratchers, floats (e.g., shoes, collars, valves, etc.), logging toolsand related telemetry equipment, actuators (e.g., electromechanicaldevices, hydromechanical devices, etc.), sliding sleeves, productionsleeves, plugs, screens, filters, flow control devices (e.g., inflowcontrol devices, autonomous inflow control devices, outflow controldevices, etc.), couplings (e.g., electro-hydraulic wet connect, dryconnect, inductive coupler, etc.), control lines (e.g., electrical,fiber optic, hydraulic, etc.), surveillance lines, drill bits andreamers, sensors or distributed sensors, downhole heat exchangers,valves and corresponding actuation devices, tool seals, packers, cementplugs, bridge plugs, and other wellbore isolation devices, orcomponents, and the like.

To facilitate a better understanding of the present disclosure, thefollowing examples of some of the preferred examples are given. In noway should such examples be read to limit, or to define, the scope ofthe disclosure.

Example

Sample cement compositions were prepared and subjected to testing forrheology and fluid loss control. The test results for sample cementcompositions having densities of 13 lb/gal (1558 kg/m³) and 15 lb/gal(1797 kg/m³) are shown in Table 1. The rheology testing was conductedusing a Fann®-35 rheometer, in accordance with API-RP-10B2 testingstandards. The fluid loss control testing was conducted using a 325-mesh(45-micron) screen and a 60-mesh (250-micron) screen, in accordance withAPI-RP-10B2 testing standards. The 500-micron slot testing was conductedon a Fann® Particle Plugging Apparatus (“PPA”) and was performed inaccordance with API-RP-13B1. The experiments on the screen arerepresentative of a permeable formation, whereas the slot isrepresentative of a fracture formation.

TABLE 1 Expt. 1 Expt. 2 Expt. 3 Expt. 4 Density of 15 15 15 13 Cement(1797) (1797) (1797) (1558) slurry lb/gal (kg/m3) Class H 677.6 677.6677.6 453 Cement (g) FLCA-1 (g) — — 1.9 3.8 FLCA-2 (g) 6.8 — 6.8 —Suspending 0.4 0.4 0.4 0.7 Agent (g) LCM (g) — 17.5 17.5 34 Clay (g) — —7.7 15 Rheology 80F 180F 80F 180F 80F 180F 80F 180F  3 8.5 13 11 17 1713 16 15  6 11.5 17 13 19 22.5 18.5 20.5 18  30 27 33.5 20 23 48 43.535.5 32  60 40 46 27 29 71 62.5 47.5 39.5 100 52 60 34 38 97.5 83 5951.5 200 85.6 90 51 57 155 129 85 69 300 113 115 64 70 204 165 106 85600 194 176 107 104 300+ 259 164 117 325 mesh 39 ml 49 ml 35 ml 87 ml(without in 30 in 5 in 30 in 30 doubling) min min min min 60 mesh No 56ml 58 ml 90 ml (without control in 5 in 30 in 30 doubling) (142 min minmin ml in 1 min) 500 micron No 44 ml 18 ml 11 ml slot on PPA control in30 in 30 in 30 min min in

In reference to the 325-mesh and 60-mesh values disclosed in Table 1,fluid loss calculations utilizing API procedures indicate 2×ml of fluidcollected within a 30-minute timeframe (doubling the amount of fluidcollected). However, for the above referenced experiments, the valuesreported are the actual number of ml(s) of fluid collected, wherein thenumber of ml(s) of fluid was not doubled. The actual number of ml offluid was reported herein because there is no API procedure for 60 mesh.Hence, the values were not doubled for the purpose of depicting an equalcomparison of experimental data.

Experiment 1 represents the control group. The control compositionincluded Class H cement, FLCA-2, and a suspending agent. The FLCA-2 was2-acrylamido-2-methylpropane sulfonic acid. The suspending agent wasdiutan. The density of the cement slurry of the control group was 15lb/gal (1797 kg/m³). Rheology and fluid loss control tests resulted in afluid loss of 39 ml in 30 minutes with the 325-mesh (45-micron) screen;142 ml in 1 min with the 60-mesh screen, which is equivalent to nocontrol; and no control with the 500-micron slot.

In Experiment 2, the composition included Class H cement, a suspendingagent, and an LCM. The LCM was a composition of petroleum coke, calciumcarbonate, graphite, and walnut hulls. The PSD of the LCM was D10:3microns, D50: 65 microns, and D90: 560 microns. The suspending agent wasdiutan. The density of the cement slurry of Experiment 2 was 15 lb/gal(1797 kg/m³). Rheology and fluid loss control tests resulted in a fluidloss of 49 ml in 5 minutes with the 325-mesh (45-micron) screen; 56 mlin 5 minutes with the 60-mesh (250-micron) screen; and 44 ml in 30minutes with the 500-micron slot.

The composition in Experiment 3 included Class H cement; FLCA-1; FLCA-2;a suspending agent; an LCM; and clay. FLCA-1 was apolyacryloylmorpholine-based polymer. FLCA-2 was2-acrylamido-2methylpropane sulfonic acid and an acrylamide-based graftpolymer. The suspending agent was a diutan. The LCM was a composition ofpetroleum coke, calcium carbonate, graphite, and walnut hulls. We Thedensity of the cement slurry of Experiment 3 was 15 lb/gal (1797 kg/m³).The resulting experimental values of Experiment 3 included a fluid lossof 35 ml in 30 minutes with the 325-mesh (45-micron) screen; 58 ml in 30minutes with the 60-mesh (250 micron) screen; and 18 ml in 30 minuteswith the 500-micron slot.

The composition in Experiment 4 included Class H cement; FLCA-1; asuspending agent; an LCM; and clay. FLCA-1 was apolyacryloylmorpholine-based polymer. The suspending agent was diutan.The LCM was a composition of petroleum coke, calcium carbonate,graphite, and walnut hulls. The PSD of the LCM was D10:3 microns, D50:65 microns, and D90: 560 microns. The density in Experiment 4 wasdecreased to 13 lb/gal (1558 kg/m³). The experimental results were afluid loss of 87 ml in 30 minutes with the 325-mesh (45-micron) screen;90 ml in 30 minutes for the 60-mesh (250-micron 0 screen and 11 ml in 30minutes for the 500-micron slot.

Therefore, as depicted in the experimental results combining fluid lossadditives and LCMs result in improved fluid loss values. For example,Experiments 3 and 4 with fluid loss additives used in combination withthe LCMs provided improved results as compared to Experiments 1 and 2that used fluid loss additives and LCMs separately. For example,Experiment 1 with only FLCA-1 did not have any control on the 60-meshscreen. By way of further example, Experiment 2 with only LCM did nothave any control on the 325-mesh screen. However, Experiments 3 and 4with both an FLCA and LCMs provided control on both the 60-mesh and325-mesh screen. Moreover, based on the experimental results, addingadditional fluid loss additive may result in greater results for fluidloss values. For example, Experiment 3 that further included FLCA-2 withFLCA-1 provided improved control as compared Experiment 4 with onlyFLCA-1.

For the sake of brevity, only certain ranges are explicitly disclosedherein. However, ranges from any lower limit may be combined with anyupper limit to recite a range not explicitly recited, as well as, rangesfrom any lower limit may be combined with any other lower limit torecite a range not explicitly recited, in the same way, ranges from anyupper limit may be combined with any other upper limit to recite a rangenot explicitly recited. Additionally, whenever a numerical range with alower limit and an upper limit is disclosed, any number and any includedrange falling within the range are specifically disclosed. Inparticular, every range of values (of the form, “from about a to aboutb,” or, equivalently, “from approximately a to b,” or, equivalently,“from approximately a-b”) disclosed herein is to be understood to setforth every number and range encompassed within the broader range ofvalues even if not explicitly recited. Thus, every point or individualvalue may serve as its own lower or upper limit combined with any otherpoint or individual value or any other lower or upper limit, to recite arange not explicitly recited.

Therefore, the present disclosure is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theexamples disclosed above are illustrative only, as the presentembodiments may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. Although individual examples are discussed, thepresent disclosure covers all combinations of all those examples.Furthermore, no limitations are intended to the details of constructionor design herein shown, other than as described in the claims below.Also, the terms in the claims have their plain, ordinary meaning unlessotherwise explicitly and clearly defined by the patentee. It istherefore evident that the illustrative examples disclosed above may bealtered or modified and all such variations are considered within thescope and spirit of the present disclosure. If there is any conflict inthe usages of a word or term in this specification and one or morepatent(s) or other documents that may be incorporated herein byreference, the definitions that are consistent with this specificationshould be adopted.

What is claimed is:
 1. A method of subterranean well cementingcomprising: providing a cement composition comprising a hydrauliccement, a combination of a first fluid loss control additive and asecond fluid loss control additive, a lost circulation material, andwater, wherein the first fluid loss control additive is different fromthe second fluid loss control additive, wherein the first fluid losscontrol additive is present in an amount of about 0.05% to about 3% byweight of the cement composition and comprises a water-soluble polymerwith repeating units comprising a 5- to 6-membered cyclic amide, whereinthe second fluid loss control additive is present in an amount of about0.05% to about 3% by weight of the cement composition and comprises awater-soluble polymer comprising at least one unit selected from thegroup consisting of a dimethyl group, a sulfomethyl group, a sulfonategroup, and combinations thereof, and wherein the lost circulationmaterial has a particle size distribution of from about 2 microns toabout 570 microns; introducing the cement composition into an annularspace surrounding a conduit positioned in a subterranean formation,wherein inclusion of the first fluid loss control additive, the secondfluid loss control additive, and the lost circulation material in thecement composition reduces fluid loss into the subterranean formation,wherein the subterranean formation has fractures with a width of fromabout 1 micron to about 800 microns, and wherein the subterraneanformation has a permeability of about 1 milliDarcy to about 250 Darcy;and allowing the cement composition to set in the annular space.
 2. Themethod of claim 1, wherein the water-soluble polymer of the first fluidloss control additive comprises a polyvinylpyrrolidone polymer.
 3. Themethod of claim 1, wherein the water-soluble polymer of the first fluidloss control additive comprises a polyvinylpyrrolidone copolymerselected from the group consisting of an acrylic acid andvinylpyrrolidone copolymer, a methacrylic acid and vinylpyrrolidonecopolymer, an acrylamide and vinylpyrrolidone copolymer, an N—N-dimethylacrylamide and vinylpyrrolidone copolymer, and combinations thereof. 4.The method of claim 1, wherein the second fluid loss control additive isselected from the group consisting of polyacrylamide, an acrylamidecopolymer, a copolymer of 2-acrylamido-2methylpropane sulfonic acid anddimethylacrylamide, acrylamide and 2-acrylamido-2methylpropane sulfonicacid monomers grafted on lignite, acryloylmorpholine and vinylphosphonicacid copolymers, and combinations thereof.
 5. The method of claim 1,wherein the lost circulation material has a particle size distributionof from about 30 microns to about 400 microns.
 6. The method of claim 1,wherein the lost circulation material comprises petroleum coke, calciumcarbonate, graphite, and walnut.
 7. The method of claim 1, wherein thecement composition has a density of about 479 kg/m³ to about 2396 kg/m³.8. The method of claim 1, wherein the cement composition has a densityof about 839 kg/m³ to about 1917 kg/m³.
 9. The method of claim 1,wherein the cement composition has a density of about 1198 kg/m³ toabout 1558 kg/m³.
 10. The method of claim 1, wherein the cementcomposition further comprises a lightweight additive selected from thegroup consisting of sodium silicate, hollow microspheres, gilsonite,perlite, and combinations thereof.
 11. The method of claim 10, whereinthe lightweight additive is present in an amount of about 0.1% to about15% by weight of the cement composition.
 12. The method of claim 1,wherein the cement composition is a foamed cement composition.
 13. Themethod of claim 12, wherein the foamed cement composition has a densityof about 479 kg/m³ to about 1558 kg/m³.
 14. The method of claim 1,wherein the subterranean formation has a permeability of about 1milliDarcy to about 50 Darcy.
 15. A cement composition comprising: ahydraulic cement; a first fluid loss control additive comprising awater-soluble polymer with repeating units comprising apolyacryloylmorpholine polymer; a second fluid loss control additivecomprising a water-soluble polymer comprising at least one repeatingunit selected from the group consisting of a dimethyl group, asulfomethyl group, a sulfonate group, and combinations thereof; and alost circulation material having a particle size distribution of fromabout 2 microns to about 570 microns, wherein the lost circulationmaterial has a particle size distribution of D10: 3 microns, D50: 65microns, and D90: 560 microns; and water.
 16. The cement composition ofclaim 15, wherein the hydraulic cement is selected from the groupconsisting of a Portland cement, a pozzolana cement, a gypsum cement, analumina-based cement, a silica cements, and combinations thereof. 17.The cement composition of claim 15, wherein the water-soluble polymer ofthe first fluid loss control additive comprises a polyvinylpyrrolidonecopolymer selected from the group consisting of an acrylic acid andvinylpyrrolidone copolymer, a methacrylic acid and vinylpyrrolidonecopolymer, an acrylamide and vinylpyrrolidone copolymer, an N—N-dimethylacrylamide and vinylpyrrolidone copolymer, and combinations thereof. 18.The cement composition of claim 15, further comprising a lightweightadditive selected from the group consisting of sodium silicate, hollowmicrospheres, gilsonite, perlite, and combinations thereof.